Early computers could only be used by persons trained in operating them. With the advent of so-called "personal computers", however, virtually everyone may have an access to a computer. To make computers more user friendly, various input devices have been introduced in different computer systems. The major popular "pointing" input device was a cursor device (such as a mouse) or a stylus device (such as a pen) for a digitizing tablet system.
A typical prior art digitizer has a tablet and a transducer/cursor in the form of a pen or a puck. To determine the general position of a transducer/cursor on the surface in an electromagnetic digitizer tablet, various methods are employed in the prior art. One common approach uses electromagnetic field sensing. In this approach, several magnetic loops (as shown in FIG. 1) are used to detect magnetic voltages, and the magnetic loops are sampled by an analog-to-digital converter under the control of a micro controller.
As we can see in FIG. 1, for a general position P of a transducer/cursor on the surface of an electromagnetic digitizer tablet, Five magnetic loops are sampled in X direction and Y direction respectively. These samples are labeled as ax, bx, . . . , ex, and ay, by, . . . , ey for X-direction and Y-direction respectively.
In this approach, assuming that the detected magnetic voltages for these samples ax, bx, . . . , ex, and ay, by, . . . , ey are Vax, Vbx, . . . , Vex, and Vay, Vby, . . . , Vey respectively, then the general position in X-direction Px would be a function of Vax, Vbx, . . . , Vex, and that in Y-direction would be a function of Vay, Vby, . . . , Vey. In other words, a general position P of a transducer/cursor on the surface of an electric magnetic digitizer tablet can be determined after the magnetic voltages are detected for these samples.
FIG. 2 illustrates a tablet coordinate system comprising many magnetic detecting loops of FIG. 1 in X-direction and Y-direction respectively. As those skilled in the art can readily recognize and appreciate, the foregoing approach could provide a position for a "pen" type or "puck" type of transducer/cursor device located in the general working area of a digitizer tablet. Unfortunately, the edge area on the surface of the tablet is an ambiguous area, no sufficient sensing voltage can be used as the formula parameter to determine the position of the edge areas (as shown in FIG. 3) on the surface of the tablet. Thus, the edge areas are wasted and not used.
FIG. 4 illustrates a simplified top view of a prior art digitizer tablet. In a conventional digitizer tablet, special functions performed for a digitizer tablet are made through menu selections which can be entered from a keyboard if desired. Nevertheless, it would be easier and more user friendly if the menu selections can be made using a "pen" type or "puck" type of transducer/cursor device.
One approach to using a digitizing tablet system combines menu and working area designations within the active area on the surface of the tablet system. This approach could provide some benefits to certain menu-driven application programs. However, there are several factors working against such uses. The primary one is cost. Another factor is that the software necessary for interfacing with other menu-driven applications may not be available.
Another approach for a user to use his cursor device on a digitizing tablet system in a manner of a mouse is the application of a mouse emulation program. In such an approach, users do not have to switch between a mouse and a tablet system. However, the emulation programs do not appear to satisfactorily emulate a mouse. Therefore, most users do use both devices depending on which device the program being used expects as its input device.
From the foregoing discussions, it can be seen that the conventional approaches have drawbacks. It is inefficient for an electromagnetic digitizer tablet system using a "pen" type or "puck" type of transducer/cursor device for providing inputs to a computer system to expand the tablet capability. There exists a strong need for having a more efficient approach for a digitizer tablet system to utilize its edge area so that the digitizer tablet system can operate more functionally on its tablet, and the edge areas of the tablet are not wasted.